四川盆地威远—资阳地区震旦系储层沥青特征及意义

CHARACTERISTICS OF THE SINIAN RESERVOIR BITUMEN IN WEIYUAN ZIYANG AREAS OF THE SICHUAN BASIN AND ITS SIGNIFICANCE

四川盆地威远—资阳地区震旦系灯影组储层中存在大量固体沥青。该区沥青产状以溶孔充填和裂隙充填为主,晶间充填次之,微粒浸染最少。根据生物标志化合物特征,可将该区沥青分为2类:一类以威117井为代表,另一类以威118井、资1井和资6井为代表。沥青产状和沥青含量的分布与储层的储集性能呈正相关关系。沥青反射率值呈2段分布,各层段演化程度相似。结合地质条件,认为该区沥青多为后生—储层沥青,属原油热裂解成因。储层沥青的含量和分布指示了原油裂解气的气源灶。沥青的产状、等效镜质体反射率值分布和生物标志化合物特征表明该区存在2期沥青,且以第2期为主,第1期较少。在此基础上,结合构造演化史,恢复了该区天然气成藏史。

There is large amount of bitumen in the Sinian Dengying Formation in Weiyuan-Ziyang areas, the Sichuan Basin. The occurrence of the bitumen is dominated by dissolution pore-filling and fracture pore-filling, with the intergranular-filling in the second and the micrograined disseminated-type in the least. Based on the biomarker characteristics, the bitumen can be divided into two types： one to Well Wei 117 as the representative, and the other to Wells Wei 118, Zi 1 and Zi 6 as the representative. There is a positive correlation between the reservoir property and the content and occurrence of bitumen. The reflectivity values of the bitumen are in two sections with similar evolution levels in different strata. With analysis of geological conditions, the bitumen in these areas was thought as epigenetic reservoir bitumen and sourced from oil-cracking. The content and distribution of the reservoir bitumen showed the gas source kitchen of oil-cracking gas. The occurrence, reflectivity value and biornarker characteristics showed that there were two stages of bitumen, and the second was majority while the first was minority. Based on these and the structural evolution history, the gas accumulation process was recovered.